Groundwater is arguably the most important substance on the planet. Without groundwater, there would be no life on earth, and groundwater is obviously necessary for human survival.
That said, groundwater is also a finite supply. There is only so much water close to the surface of the planet, and only a small fraction of that is accessible to humans. Exactly how much groundwater there was on Earth, and where it was actually located was not well known until now.
For the first time since a very rough calculation of the global volume of groundwater was undertaken almost four decades ago, a team of hydrologists from across the globe has used hard data to estimate the Earth’s total supply of groundwater. The new groundwater study was supervised by Dr. Tom Gleeson of the University of Victoria with a number of co-authors at the University of Texas at Austin, the University of Calgary and the University of Göttingen (Germany), and was published Monday, November 16th in Nature Geoscience.
Groundwater not a renewable resource
The researchers say the most important part of the new groundwater study is the “modern” groundwater. The data suggests that under 6% of groundwater in the upper two kilometers of the Earth’s crust is renewable within a human lifetime.
“This has never been known before,” Gleeson noted. “We already know that water levels in lots of aquifers are dropping. We’re using our groundwater resources too fast–faster than they’re being renewed.”
Given the growing global population and demand for water, the new research provides important data to water managers and policy makers, as well as scientists involved in hydrology, atmospheric science, geochemistry and oceanography to improve sustainable management of groundwater resources.
The study used multiple datasets, including data from close to a million watersheds) and more than 40,000 groundwater models, and came up with a final estimate of a total volume of 23 million cubic kilometers of total groundwater, of which around 0.35 million cubic kilometers is under 50 years old.
Statement from groundwater study researcher
“Intuitively, we expect drier areas to have less young groundwater and more humid areas to have more, but before this study, all we had was intuition. Now, we have a quantitative estimate that we compared to geochemical observations.” explains Dr. Kevin Befus, who undertook groundwater simulations as part of his doctoral research at the University of Texas, and is now a post-doc fellow at the USGS.
